Electromagnetic relay



Sept- 15 1952 R. E. H. CARPENTER 2,611,063

ELECTROMAGNETIC RELAY Filed Aug. 28, 1950 2 SHEETS-SHEET 1 AttorneySept. 16, 1952 R. E. H. CARPENTER ELECTROMAGNETIC RELAY 2 SHEETS-SHEET 2Filed Aug. 28, 1950 atentec Sept. 16, 19512 ELECTROMAGNETIC RELAY RupertEvan Howard Carpenter, South Croydon, England VApplication August 28,1950, Serial No. 181,903 In Great Britain September 2, 1949 v K 14Claims.

This invention relates to the mounting and control of the contacts ofelectrical .circuit- 1 controlling apparatus such as electrical switchesand circuit-breakers of all kinds but it has particular reference to thecontacts of electromagnetic relays, and is more particularly concernedwith the construction and control of the vibratory armature and themounting and sup- ;port of the passive or side contacts of such relays.A fundamental problem encountered in the design of electromagneticrelays is that of pre- Wenting Ibouncing orchattering of the contacts,.and this problem becomes more difficult of solution as the contacttravel, and hence the velocity of the moving contact at the instant ofimpact, is increased.

, Two types of bouncing may be observed, one

. of comparatively low frequency in which typically the first bounceoccurs some one to two milli- 1 seconds afterthe first impact, theduration of theiirst break being a substantial fraction of amillisecond, and another of much higher frequency in which the contactsseparate, for ex- ,ample, some thirty to fifty microseconds after wearmay be quite serious.

The present invention aims at eliminating both these forms of contactbouncing, and it is especially useful in relays having long contact.traveL although not, of course, limited to electromagnetic relays ofany kind.

In accordance with the present invention, this -is attained by providinga mass mounted on one or both'of the supports of the pair of contacts tobe controlled in such a Way as to be able to move relatively to thatsupport due to the inertia ofthe mass. operating at the instant ofchange of velocity caused by the closing of the pair of contacts and therelative movement is restrained mainly or largely by the action offorces set up by friction occurring between bearing surfaces shaped toslide smoothly one upon another or by fluid friction or by frictionoccurring Within a -deformable body. In the case of an electro-Vmagnetic relay with a vibratory armature, the

inertia mass may thus be mounted on the arma- 'ture -or on the supportor supports of the passive contact or contacts or both. The frictionalv'ffc'irces may be exerted on` a surface of the mass or within a body ofdeformable material coupling the mass to the respective contact supportso that a drag is applied to the contact support and the contacts aremaintained closed in spite of any tendency to bouncing due to theelasticity of the parts. l

By an electrical analogy, the frictional coupling of the inertia mass toits contact support is of the nature of resistance coupling rather thancapacity coupling and the restraining force operates immediatelydeceleration of the contact and its support begins. The system is unlikethat of a mass mounted on a compliant support and the latter would notresult in the desired reduction or elimination of contact chatter.

If the frictional drag is exerted through an external surface of themass, in the case of the armature contact of a relay, it may be appliedto the end surface or a side surface of the armature or of a memberfixed to the armature. The force holding the frictional surfaces inengagement may be provided either by a spring pressing the sliding massagainst the armature or, by making the sliding mass of magneticmaterial, when magnetic attraction, due, for example, to stray flux fromthe armature, may provide the necessary force. The sliding surfaces maybear directly upon one another, or an interposed layer, such as awasher, having the desired frictional and wear-resisting characteristicsmay be employed, a synthetic resin impregnated with graphite or somesoft metal having been found suitable. When the mass is springheld, thespring may be made adjustable so as to control the frictional force.

In cases in which the velocity of transit of the armature is highlyVariable, and especially when it is different in the forward and returndirections of its movement as in single-current working, there is somedanger of the sliding mass hitting its stop, and this impact beingtransmitted to the armature and hence to the contacts, may itself tendto cause bouncing. In order to reduce this effect, a spring or springsmay be employed tending to centralise the sliding mass with respect toits stop or stops, or the latter may be springy. Thus, for example, thespring may be a cylindrical coiled compression spring housed within theinertia mass and bearing on a seating in the mass at one end andconstrained by a fixed member at the other end. Then, when the massslides relatively to the armature, the spring is deformed and inrecovering,'tends to centralise the mass. The fixed stop engaging oneend of the spring may comprise the head of a stem projecting vfrom thearmaf pads.

ture and also passing through a clearance hole in the inertia mass andthereby acting as a limit stop for the sliding movement. Of course,other centralising means suificiently gentle in action to permit thenecessary sliding can be adopted, such as a coiled compression spring ofconical conguration.

If the frictional dragy is exerted within a body of rubber-like materialwhich should exhibit considerable hysteresis, the latter is deformed onthe mass tending to overshoot the armaturev and thereby energy isexpended yinthematerialv` The body may due to its mechanical hysteresis.then consist for example of `a pad of soft material, such as felt ornatural or artiiicial rubber* cemented to the armature and surmounted bya metal weight forming the inertia.'V mass and clamped between the saidpad of material and a second similar outer pad of soft material. A stemmay project up from the armature through Ythe adjacent pad and passesthrough a clearing holle in.` the metal mass so that the latter overfthearmature face. The frictional drag or damping may be provided byemploying a'ring of 'felt or other'rubber-like material encircling anextension of the said outer 4part ofthe arm sothat'as vibration' isimpartedA to the` cantilever arm, the said ring is deformed incompression- Figure 4 is a plan of Figure 3;

Figure 5 is an elevation; and

Figure 6 is a plan corresponding respectively' to Figures 3 and 4 butshowing a modified form of the armature damping member;

Figure 7 is a sectional edge elevation of the upper part of an armatureshowing another form or" the anti-bouncing device; Y

Figure 8 is a sectional elevation on the line VIII- VIII in Figure 9;and

Figure 9 a plan of another form of damping member employing an inertiamass including A' deformable rubber;

tension or shear Vand provides the 'damping -`action. y

Q'Again Va pin may'extend from the said ex- -tension vof the outer partof the arm towards vthe relay frame and may itself be encircled byvajring of the deformable material enclosed in ramletal ring which formsthe inertia mass. VIn l'another form, the spring arm bearing the ycon- Atact isextended and inclined inwards towards the relay frame at an angleand is straddled r"bya vstrip of; deformable material which isencasedina metal strip which forms the inertia `mass. Yet again the outer partof the ,contact spring arm may be shaped with a'friction surface and vbelooped intoV a spring bearing the iertia'mass and pressing itinto'contact with thesaid frictionjsurface. Then on impact-of thearmature against the passive 'contact,jt`he inertia mass is restrainedby the frictional force applied to it' and acts to prevent the passiveVy accordance with the invention will now be more fully described withreference to the accompanying drawings, in whichn Figure 1 is a sideelevation ofthe upper part cfa relay Vfitted withanV armature dampinglmemberaccording to the invention;

Figure 2 is a plan of the same; y

' Figure 3 isv an venlarged elevational, partly in section, of the upperpart of the armature and its damping member; l

Figure 10 is a side elevation; and vFigure 11 a section on the lneXI-XIin Figure 10 of one form of the improved stationary orA passive contact;Y

Figure 12 is a side elevation; and Figure 13 a section on the lineXIII-XIII in Figure 12 of another form of stationary contact;

VFigureli'is a side elevation; and Y Figure '15 aV section on the lineXVLXVr-in Figure 14 of'yetel third form of stationaryfcontact; while ivFigure 16is a side elevation; and Figure V17a plan of 'still'anotherformofestationary contact.

Referring'firstto Figures A'l to 4 rof therdrawings, lthe invention isapplied to an electromagnetic relay as described in the specificationofmy United States Patent No. 2,559,399. Ini Figures l`4 and 2, `thepermanent magnets are seen at I, the armature "2 bears thecontacts 3vwhich 'engage the stationary Ycontacts il supportedon the frame members5. l v Y The'inertia mass't lcarried by the "armature is shown in morevdetail in Figures 3`and"4"and 'is in the jformof a'hollow cylinder.

y A Y'screwthreaded `stemfi is adjustably tapped rinto the upperend ofthe'armature 2 andis secured by a lock-nut 8 of Duralumin which consists'fof-fa hexagonal shank 9- and a at circular` platform I0. On Athe topVof the'latter is --supportedfa washer II which, in 'thisvexe'miple,'consists r`of the phenol-formaldehyde resin'knownas Catalifnand is impregnated with graphite. The cylindrical mass Sjrests on thewasher II yand'fsur- 1 rounds the stemAI which passes throughaclearinghole I2 in the base vof the massfj Afccnidal Ycoiledcompression spring Iisjhoused'- in'the Lcylinder E and abuts at thebotto'mon the vupper 'surface of vthe vbase Vof the'jcylinderV 6andf'fat "the-top against the* head Illfoftheste'm 7. vThe spring I3thus pressesthejmassv r6fagainstthe washer II and 'the' latteragainstwtheplatfrm I il fixed' to the armature 2 with an adjustablepressure. "In order-'to adjust'this pressurefthe `lock-'nut 8 isloosenedfby'grippingithehexagonal vshank 9 and the stem I screwed uprdown'and then lockedI by' tightening `the lock-nut "8.

In'operation, when the' armaturel "i'sfdecelrated by one of its contacts@striking-the coacting passive contact'ii, the mass 6 tends to'continueits movement thus exertingfa'frictional vdrag on theV platform I3'andthe armature-2,

thereby resisting any tendencyA for thel armature `2 to bounce away fromthe contacta. During this time, the spring I3 is distorted? but-when theparts come to rest; it recovers and centralises the mass B again. p t

'The mountings 0f the passive por 'sidev contacts Aare asshown in moreVdetail-Vin Figures lean/d '11. Each Contact,l 4 carriedA on a stm; iiatcantilever spring I5 rivetted `to one of fthe? relay `15 frame members'Sat. I6.. The spring I5.has;parts I1; and I8l at either endV paralleltolthexfaces of the armature 2 and `of theframe member 51 and anintermediate-part I9 extendingat-.anangle to the parts I1 and I8 suchthat the line-between the contact 4v and the effective hinge` at'thebottom end of the part I9 is at about 45 degrees to the face of theframe member 5. The Vpart I8 carries the stationary contact 4. The partlI8 is extended and turned over at 2| towards the frame member 5. A stripof neopreneA 22 is bent to embrace thepart 2| and is. retained inposition by an encircling strip 23 of metal which serves as the inertia,mass vand when the passive contact 4 is struck,k deforms thenneoprene22 isothat the energy of any-vibration -offlthe spring I6 y is absorbedas hysteresis` in the Arubber strip 22 andthe vibration is limmediatelyldamped out.`v v- -1 In Figures and 6, a modified device isshcwn whichmay replace lthe inertiamass 6 shown in Figures 1 to 4. Again aVscrew-threaded stem 1 is adjustably tapped into the end of the armatureI and is surrounded by a washer 24 seated on the end of the armature 2,a synthetic resin washer 25, the boss of a bracket arm 26, anda furthersynthetic resin washer. 21. This pack is adjustably pressed together byva cylindrical coiled spring 28 abutting at its lower end against a cup29 and at its upper end against an enclosing cap 30; the wholerbeingheld down by a nut 3I screwed on to the stem 1 and enabling the pressureto be adjusted., The bracket arm 26 supports the inertia mass`32 whichis a cylinder threaded over a second stem 33 and held by nuts 34.

In this case, when the armature 2 is decelerated, the mass 32 tends tocontinue its movement and, as a result, the bracket arm 26 exerts africtional drag on the armature 2 through the washers 24, 25 and 21 witha similar result as in Figures 1 to 4. The actual movement of thebracket arm 26 relatively to the armature 2 in either direction islimited by a pair of stops consisting of resilient arms 35 which aresecured by a further nut 36 and yield under the force of the mass 32 butrecover to centralise that mass when the parts come to rest.

It is obvious that the device shown in Figures 5 and 6 could be attachedto either edge surface of the armature 2 instead of to its end surface.

In the further form shown in Figure '1, a small entirely closed cylinder53 is xed to the top surface of the armature 2 and contains alooselyfitting slidable piston 54 which forms the inertia mass. Thespaces 55 on either side of the piston 54 are filled with light oilwhich provides the frictional force restraining the movement of thepiston 54. Conical springs 56 at either end of the cylinder 53 serve asstops for the piston 54 and assist in centralizingr the latter.

Yet another variant is shown in Figures 8 and 9 in which a stem 'I isagain screw-threaded andV tapped into the end of the armature 2. Acircular pad 31 of felt encircles the stem 1 and rests on a washer 4Iseated on the end of the armature 2. On the pad 31 rests a metal weight38 which forms the main inertia mass and has a clearing hole 39 throughwhich the stem 1 passes. A second pad 40 of felt rests on the weight 38and the three members 31, 38 and 40 are pressed on to the end of thearmature by a top washer 4Ia and nuts 42, the pad 31 being preferablycemented to the Washer 4I and to the weight 38 and the pad 40 also beingcemented to the weight 38. In this case, when the armature isdecelerated, the Vweight 38 continues itsumovenient-.but there is nofrictional sliding of one member on another,^- AOn the other hand,V thepads 31 and .40 are deformed withinternal friction which restrains themotionyof the weight 38.and-thus prevents bouncing. of the contacts.

In Figures l2 and '13, a variant of the mount,- ing for the stationarycontacts is shown. 'Ifhe contact 4 is mounted on a cantilever spring I5as in Figure 10 but the part I8 of the spring is extended and isencircled by a relatively massive ring 43 4of felt. The effect, however,is similar to that of the form shown in Figures 10 and 1,1. In Figures14 and 15, the mounting for the stationary contacts Vis yet againvaried. In this case, the part I8 of the cantilever spring I5 yhas aheaded pin 44 extending at right angles to wards the relay frame member5. A ring of felt 45 encircles the pin 44 to which it is fixed byadhesive and thering 45 is encased in a metal ring 46 which acts as theinertia mass. Otherwise, the operation is the same as in the case ofFigures 10 and 11. l

Finally, in Figures 16 and 17, the part I8 of the cantilever spring i5which bears the station-l ary contact 4 is turned at right angles at 41into thevertical plane and vbroadened into a platform 48. A narrowextension 49 is looped tothe side at 50 and turned over into contactwith the platform 48 at 5I. At that point, it carries the inertia mass52 which is a cylindrical weight. The spring loop 50 is set so that itcauses the mass 52 to be frictionally coupled to the contact 4 throughlthe platform 48 on the supporting arm I8.

What I claim is:

1. In an electric switch having a pair of cooperating contacts, one ofwhich is mounted upon a movable support, the combination of an inertiamember mounted upon said movable support and being movable with respectto said support under the impact of a sudden engagement of saidcontacts, means providing a frictional coupling between said inertiamember and said support for applying frictional drag on said support bythe relative movement of said inertia member upon sudden closing of saidcontacts, and resilient means interposed between said inertia member andsaid support and tending to limit said relative movement.

2. A switch according to claim 1 wherein said movable support comprisesan armature member carrying the movable contact.

3. A switch structure according to claim 1 wherein said movable supportcomprises a yieldable member carrying a passive contact.

4. A switch structure according to claim l wherein said frictionalcoupling is provided by sliding contact between a surface of saidinertia member and a surface on said movable support, and includingspring means for holding said surfaces in contact under pressure.

5. A switch structure according to claim 4 and including agraphite-impregnated washer interposed between said surfaces.

6.. A switch structure according to claim 1 wherein said frictionalcoupling means comprises a body of deformable material connecting saidinertia member with said movable support and having appreciable internalresistance.

7. A switch structure according to claim 1 wherein said inertia membercomprises a body of deformable material mounted upon said movablesupport and being connected with said support by a resilient portionthereof having an apprecif ableinternalfresistance,whereby..zsaid.resilient :portion forms: alIrietiona-l Y couplingsbeimveens'aid body-.andsaidsupport and opposesrelativefmovment-betweenssaid bodyaand saidsupport.`

-fAnl electric switch structure .A accordingVV V.to claiin'lband"includingA a` fixed stop for. limiting relative movement ofV saidinertia.V member with respectftof-said supportf and-wherein said.resilientmeansfactsl upon said-inertiamember inl a direction to opposemovement of` said member towards saidstop.v l A y 9.In an electricswitchrhavlng armovable contactbarriedby a movablevarmatureranda passivecontact supported upon` a cantilever'spring- `and being-yieldablymovable upon engagement-by said movable contact; thecombination-oaninertia member supported" upon said cantilever spring and vbeingAmovable' withA respect 1 to saidv spring under'the-impact of suddenengagement oflsaid contacts, and *means` providing a frictional couplingbetween -said inertiav member and Asaid springV for applying africtional-dragfon said springby the relativemovement of said inertiam"ember. y

'lOA switch sinfuctureV according to `claim 9 wherein saidinertia membercomprises aV body of resilient'deformablematerial mounted Aon anextension' of said spring:

` Y 'T111' Aj switchr structure'according to vclaim 10 andfincluding ametal member surrounding said looliy'cjzf` Vdeformable material. i' j1.2i" 'Ag 'swit'chj structure. according tov `claim' 9 y i in 'said'inertia. member isY carried byarr. ex-

tension arm' .offthe cantilev'efs'ringturned .back

' sowthatithe inertiamembertis pressed to: bear l frctionally, on.. the.cantilever spring.

alever arm carrying''saidinertia member on'one of said arm to'saidimovable supportV for lpivotal movement about an axis arrangedtransversely c BEYFERENCESQITED. The"` ollowing;V references'. are. ofrecord `inthe file of this -patent:Y .c i A ,ly

vUNITED STATES PATENTS Nilmber v Name v y' Date v L 2,540,854VVWoestemeyer Feb. 6, 1951 Number Country D'r/ itel f 376.5112" GermaniJune-Salm

